The objective of this project is the continued development and evaluation of statistical methods for use in research related to drug use and the Acquired Immuno-deficiency Syndrome (AIDS). A collaborative team drawn from five university centers will undertake research studies to respond to the need to provide information on the AIDS epidemic which makes full use of available data. Statistical methods which allow description of the time-dependent multifactorial aspects of the natural history of AIDS will be developed and applied to data on intravenous (IV) drug abusers who are infected with the human immunodeficiency virus (HIV). Relative risk regression models will provide a methodologic framework for this research. Topics of specific interest will be (i) the development of models for immunological markers of HIV disease and their relationship to clinical outcomes in IV drug abusers, (ii) estimation of the time of HIV infection and the probability of developing AIDS after infection in IV drug abusers, (iii) estimation of seroprevalence and incidence in IV drug abusers, (iv) models for studying the role of cofactors that affect vulnerability and transmissibility of HIV, (v) mathematical modeling of AIDS risk and transmission among IV drug abusers and the heterosexual population. Other areas to be considered include AIDS case projection methodology, analysis of correlated categorical data and work on data from international sources. Furthermore the analysis of data arising from studies of AIDS in the research centers will continue to direct research focus as well as provide the opportunity to test methods and computer software which are developed as part of this research.